1. Field of the Invention
This invention relates to a photonic crystal and a surface emitting laser using such a photonic crystal.
2. Description of the Related Art
In recent years there have been a number of reports on applications of a photonic crystal to a semiconductor laser. Japanese Patent Application Laid-Open No. 2000-332351 describes a semiconductor light-emitting device (surface emitting laser) produced by arranging an active layer containing a light emitting material and forming a two-dimensional photonic crystal near the active layer. It is a type of distributed feedback (DFB) laser. Cylindrical holes are periodically arranged in the semiconductor layer of the two-dimensional photonic crystal and the refractive index distribution thereof illustrates a two-dimensional periodicity. Light generated in the active layer resonates to form a standing wave and give rise to a laser oscillation due to the periodicity. It operates as a surface emitting laser as light is taken out in the direction perpendicular to the surface by primary diffraction.
U.S. Pat. No. 6,055,262 discloses a photonic crystal surface emitting laser having a configuration different from the one described in the above Japanese Patent Application Laid-Open No. 2000-332351. It is a sort of vertical cavity surface emitting laser (VCSEL) in which at least one of the pair of mirrors forming the resonator is formed by a periodic structure (photonic crystal). Light having a specific wavelength gives rise to a phenomenon referred to as GR (guided resonance) out of light striking into the photonic crystal in the directions from out of the plane to the inside and is reflected at a high reflectance (see V Lousse et al.: Opt. Express, Vol. 12, No. 8, p. 1575 (2004)). In short, a photonic crystal operates as a mirror having a high reflectance in the photonic crystal surface emitting laser.